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i. 7-Eleven/Stockton 4 May 1990 In order to initiate -the assessment of the lateral and vertical-extent of soil and groundwater impacted by gasoline hydrocarbons, groundwater-monitoring wells MW-•1, MW-2, MW-3, and MW-4 were installed on May 6 and 7, 1986. In late May 1986, five additional monitoring wells were installed (MW-5, MW-6. MW-7, MW-8, and MW-9) , and sampling of the monitoring wells and nearby domestic wells was initiated. These preliminary hydrogeologic investigations identified gasoline hydrocarbons adsorbed within the vadose-zone soil, dissolved within the groundwater, concentrated as free-floating separate-phase hydrocarbons (free product) , and volatilized as vapors. The discovery of free product in monitoring wells MW-1 and MW-4 prompted the initiation of a groundwater remediation / abatement program. Initial work involved periodic hand bailing w of free product as requested by the San Joaquin County Vocal Health District. In early July' 1986 a. small-diameter.; double- pumping system was installed in MW-4 to control the continued migration of free product and to collect it from the well. In an attempt to obtain increased control on the free product and dissolved--phase hydrocarbon plumes beneath the site, three recovery wells were installed between October and November, 1986. One 4-inch-diameter recovery well, PW-1, was installed on the periphery of the site between monitoring well MW-9 and the 1 domestic well at 9135 Connie Avenue. This well (PW-1) was installed to prevent the migration of dissolved hydrocarbons into domestic well 9135. Another 4-inch-diameter recovery well, P.W-2, was installed downgradient and off site between domestic well 8968 and the previously installed monitoring well MW-r. This pumping well was installed in the event that it would be needed to prevent the migration of dissolved hydrocarbons toward domestic well 8968. 14 GROUNDWATER TECHNOLOGY.INC.